1. Field of the Invention
The field of the invention relates to a measuring roll for measuring the tension of a strip passing thereover, said tension being related to the shape or flatness of the strip.
2. Brief Description of the Prior Art
In cold rolling sheet stock, the amount of work performed on a sheet cross section determines the quality of the product. If excess work is performed in the center of the stock, the center elongates longitudinally more than the edges and therefore buckles in the center. The converse is true if excess work is performed at the edges.
Many factors, such as quality of input stock, localized heating of the mill roll faces, or deflection of the rolls, influence these cold work variations. Since the strip is reduced not only by roll compression but also by the high tensile loads applied with the coiler, these defective areas are difficult to detect until the coil is complete. The defects that are detected during rolling are compensated for through manual adjustment of the rolling mill or through the application of coolant to the roll faces. It is important that defects be substantially reduced, if not eliminated entirely, because those areas of the sheet stock outside the acceptable flatness limits must be scrapped with resulting economic loss.
Shape sensing rolls have been developed to monitor the rolling mill output. U.S. Pat. No. 3,499,306 discloses one such roll which is pneumatically operated. Mechanical bearings have also been employed for this purpose. Both types operate in conjunction with control systems for making adjustments in the rolling mill in response to changes in detected strip tension.
Metal strip on the delivery side of a mill is tensioned at as much as 1,000 lbs. per inch of width, nominally 25,000 to 50,000 lbs. The shape sensing roll is positioned to provide a selected wrap angle of the strip thereover. A component of the strip tension then becomes a reaction force on the roller face. The roller is divided into segments that react independently to measure this tensile force component at a given point across the sheet. If these forces are known, adjustments can be made to the rolling mill to level out the force differentials using two techniques: roll bending and roll temperature control (by selective coolant spray).
The presently available measuring rolls have various shortcomings which may tend to limit their application to various measurement applications. Pneumatic bearings, for example, have an inherently low load carrying capacity which requires delicate instrumentation and control components to achieve the intended function.
Load cell measuring equipment is characterized by non-linearity, dead band, hysteresis, and minimum load levels for accurate measurement. Such equipment includes a series of ring assemblies mounted to a common shaft. Each ring assembly includes a ground ring press fit onto the outer roll of a roller bearing. The inner bearing race is press fit to a collar which is machined to accept a load cell contacting the inner bearing race. Vertical loads applied to the outer ring are transmitted to the load cell and directly monitored.
In view of the above, it is an object of the present invention to provide a system which is capable of successfully operating under a wide range of loads with a high degree of accuracy.